#include <stdio.h>

// main rec funcion
int check (int dest, int size, int friends[size][2], int checked[], int next) {

    // if it found dest, returns 1
    if (dest == next) {
        return 1;

    } else {

        // otherwise, it iterates for every line of input. Grabs a number checks if its
        // related to another and calls this function again. Does this again till it finds
        // dest. If all numbers are visited and current dest can't be found it returns 0
        for (int i = 0; i < size; i++) {

            if (checked[i] == 0) {
                if (friends[i][0] == next) {
                    checked[i]++;

                    if (check(dest, size, friends, checked, friends[i][1])) {
                        return 1;
                    }
                }
                else if (friends[i][1] == next) {
                    checked[i]++;

                    if (check(dest, size, friends, checked, friends[i][0])) {
                        return 1;
                    }
                }
            }
        }
    }
    return 0;
}

int main (int argc, char *argv[]) {

    // declaration and assigning
    int size, first, sec;

    scanf("%d %d %d", &size, &first, &sec);

    int friends[size][2], checked[1000];

    // scans size lines of input
    for (int i = 0; i < size; i++) {
        scanf("%d %d", &friends[i][0], &friends[i][1]);
    }

    // calls main recursive funcion, prints appropiate output
    if (check(sec, size, friends, checked, friends[0][0])) {
        printf("YES\n");
    } else {
        printf("NO\n");
    }
}